A method includes: determining, by a terminal device, that assistance information of the terminal device can be sent to a first network device through a signaling radio bearer (SRB)3, wherein the terminal device is connected to at least two network devices, and the first network device is a secondary network device in the at least two network devices; and sending, by the terminal device, the assistance information to the first network device through the SRB3, wherein the assistance information is used to indicate a configuration expected by the terminal device or service information of the terminal device.